1. Field of the Invention
The present invention relates generally to an apparatus and method for separating articles into batches. The invention relates specifically to an apparatus and method for separating a stream of lapped signatures into discrete batches of lapped signatures.
2. Description of the Related Art
When articles are conveyed in a continuous stream, it is often necessary to separate the stream into discrete batches of articles for packaging or other purposes. This is particularly important in the field of newspaper printing. For example, while newspaper presses can produce signatures at rates in excess of 70,000 copies per hour, some downstream equipment, such as tying machines, cannot keep up with such speeds. Other procedures, such as placing top sheets with delivery information on the bundles, also are difficult to accomplish successfully and reliably at high production rates.
Dividing the high speed press output of lapped signatures into two separate streams can reduce the downstream load by 50% per line, and permit slower downstream equipment to successfully and reliably operate while accommodating high press output rates. Further divisions of the press output result in further reductions in the downstream load.
One way to divide the press output is to use gripper conveyors which have a series of grippers. Since each gripper carries an individual signature, gripper conveyors have the inherent ability to divide the stream of signatures by dropping individual signatures off at multiple locations.
Another way to divide the press output is to use belt conveyors which split the stream into discrete batches. In comparison to gripper conveyors, belt conveyors have the advantage of substantially lower cost and maintenance. However, there are drawbacks in attempting to use belt conveyors to divide a stream of signatures. Unlike gripper conveyors, belt conveyors do not have the ability to divide a stream of signatures on a product by product basis. In addition, it is difficult to use belt conveyors to divide a high speed stream of lapped signatures into discrete batches without causing the signatures to pile up, changing or disturbing the lap between signatures, or stopping or varying the flow of signatures at the infeed and at the outfeed.
For example, one known batching device uses an element which penetrates the stream of articles on a belt conveyor to restrain a group of articles and create a discrete batch. Another known device uses two conveyor belts; one conveyor belt restrains a portion of the stream of articles and creates a gap in the stream between the restrained portion and the portion ahead of the restrained portion which proceeds on the other conveyor belt. Both of these devices have the drawback of causing articles in the restrained portion to pile up behind the elements which intercept and restrain the stream.
Another batching device receives a series of articles which fall from an infeed conveyor. The batching device includes a first conveyor having an endless transporting portion which is positioned below the infeed conveyor. The batching device also includes a second conveyor, having a discrete transporting portion which travels on a path above the first conveyor and between the first conveyor and the infeed conveyor. The second conveyor intercepts and initiates the formation of a batch from articles which otherwise would fall on and be transported by the first conveyor.
Such an arrangement requires the transporting portions of the various batching conveyors to be on different levels, with the second conveyor directly above the first conveyor. The arrangement also requires the articles to fall during infeed and changes the spacing or lap of the articles when they fall from the infeed conveyor onto the batching device. It additionally requires the articles to be transported on the batching conveyors at different levels and undergo a change in elevation during discharge to an outfeed conveyor. Finally, it discharges the initial portion of the batch at a slower speed than the final portion of the batch.
The use of conveyors positioned at different levels substantially increases the possibility of misaligned and jammed articles. It presents further problems by requiring wide spacing between the endless conveyor of the batching device and both the infeed and outfeed conveyors to accommodate the cycling of the second conveyor around and directly above the endless conveyor.
Yet another device uses a constant speed conveyor to transport a stream of articles and uses a second conveyor to elevate a portion of the stream higher than the level of the constant speed conveyor. The second conveyor transports the portion of the stream which it carries at a speed which is higher than the speed of the constant speed conveyor. The difference in speed introduces a gap between the signatures traveling on the different speed conveyors. Since this device uses conveyors traveling at different speeds at the outfeed, it causes some batches of signatures to travel at high speeds at the outfeed, and other batches of signatures to travel at low speeds at the outfeed. Such an arrangement requires the two batches to be delivered to different outfeed locations or requires changing the speed of the outfeed conveyor repeatedly between higher and lower speeds.